This invention relates to roll bars used on pick up trucks to prevent a catastrophic crushing action on the roof of the truck cab in the event of a rollover accident. Such roll bars include crosspieces extending horizontally behind the cab at or slighyly above the roof plane. In some cases external lights are mounted on the crosspieces to provide forward night vision beyond the zones covered by conventional headlights (which are considerably closer to the ground than the elevated lights on the roll bar).
Under some circumstances it may be desirable to lower the roll bar, e.g. to protect the overhead lights from contact with low hanging branches of trees near the path being taken by the truck.
The present invention relates to a retractable rollbar mechanism that can have a raised position wherein the crosspiece is elevated above the roof plane, or a lowered position wherein the crosspiece is below the roof plane. The mechanism includes a fluid-operated power unit installable on the bed (bottom wall) of the truck cargo box. The output member of the power unit is operatively connected to a vertically movable portion of the rollbar mechanism for raising or lowering purposes.